The present invention relates to wireless mesh networks, and more particularly the use of such networks within lighting systems.
Wireless mesh networks that control lighting or other devices are well known. A mesh network is made up of a number of short-range, low-cost nodes. The nodes communicate with one another, typically using a mesh network protocol that involves broadcasting a message and having all nodes rebroadcast all received messages.
Mesh networks have limitations. Nodes rebroadcasting at the same time in a small region on the same channel may interfere with each other. The more nodes rebroadcasting, the more interference and the smaller the chance that a message will be heard. Ultimately, the interference may result in unacceptable message latency or in some nodes not receiving the broadcast messages at all. This effect is called the dense mesh network dilemma.
Attempts have been made to reduce or eliminate the negative effects of a dense mesh network. However, none of them have proven to be satisfactory. Limiting the frequency and length of messages may lessen the negative effects, but it is impractical in some applications, such as time sensitive or data heavy applications. Of course, the distance between nodes may be increased to alleviate the dense nature of the mesh network, however, many applications require closer spacing than is feasible. The number of radio channels used in the mesh network protocol may be increased to reduce the negative effects of a dense mesh network. However, hardware which communicates over multiple channels typically is more complex and costly.
All of these attempts to eliminate or reduce the dense network density dilemma require compromises that may be unacceptable in some applications.